RFID systems are well known in the art. Such systems include relatively large packages containing battery powered transmission/receiving circuitry, such as the identification system disclosed in U.S. Pat. No. 4,274,083, to passive systems in which the transceiver receives its power from the base station or interrogator, such as the identification system disclosed in U.S. Pat. No. 4,654,658.
A typical RFID system is made up of reusable tags fixed to or embedded in product carriers, antennas that interrogate the tags via a RF link and a controller. The host (or computer) system interfaces with the controller and directs the interrogation of the tags.
RFID tags provide effective means of identifying, monitoring and controlling materials in a closed loop process. In the factory, tags are employed as the transport mechanism between "islands of automation," providing a record of each process which can be acted upon immediately or downloaded later for analysis.
The tags can be powered by an internal battery (i.e., an "active" tag) or by inductive coupling (i.e., a "passive" tag). Passive tags have zero maintenance and virtually unlimited life. The life span of an active tag is, however, limited by the lifetime of the battery, although some tags offer replaceable batteries.
RFID tags are packaged in a variety of forms and are fastened by a multitude of means. The tags are typically encapsulated for durability against shock, fluids, dust or dirt. Although such tags are immune to most environmental factors, they can, and in many instances will be, adversely affected by high temperature environments.
It is, therefore, an object of the present invention to provide a RFID tag having the capability of operating over a broad range of temperatures.
It is another object of the invention to provide a RFID tag which is capable of operation in harsh, high temperature factory environments.